If you participate in retrospective rating, either as an enrolled employer or a group sponsor, the rules in effect on the first day of a coverage period are the rules that will apply to you for that coverage period, even if some of these rules are changed later.
Wash. Admin. Code § 296-17B-040
Statutory Authority: RCW 51.16.035, 51.16.100, 51.04.020(1), and 51.18.010. 10-21-086, § 296-17B-040, filed 10/19/10, effective 11/19/10.